Update cheatsheet.fr.md

12.temporary_ins/40.classical-mechanics/30.n3/30.point-kinematics/20.overview/cheatsheet.fr.md

@@ -248,7 +248,7 @@ RÉSUMÉ
     <br>
     **$`\begin{align}
     \left.\dfrac{d\overrightarrow{e_{\theta}}}{dt}\right\vert_{\mathscr{R}}=&\dfrac{d(\cos\theta\,\cos\varphi)}{dt}\,\overrightarrow{e_x}\\
-    &+\dfrac{d(\cos\theta\,\sin\varphi)}{dt}\,\overrightarrow{e_y}+\dfrac{d(-\sin\theta)}{dt}\,\overrightarrow{e_z}
+    &+\dfrac{d(\cos\theta\,\sin\varphi)}{dt}\,\overrightarrow{e_y}-\dfrac{d(\sin\theta)}{dt}\,\overrightarrow{e_z}
     \end{align}`$**   
     <br>
     **$`\begin{align}